Modulation



Oct. 2 9, 1940. R. HoFl-:R Er AL IODULATION Filed May l', 1957 2 Sheets-Sheet 1 v1 r.. n n ww. n

Riff/'HER Ffm Parar/AL E smh wmp n mwa N EMM/ v L .T NMOKT nu@ A RR Oct. 29, 1940; R, ||QFERy Er AL 2,219,449

V MUDULATION Filed May l 1937 2 Sheets--SheetI 2 Y RUDLF GURTLER ATTO R N EY Patented Oct. 29, 1940 UNITED STATES I MGDULATION Rudolf Hofer many, assignors Drahtlose Application May 1,

In Germany In all methods predicated upon modulation of an input stage of the transmitter, the power stage which takes the major part of the energy operates at low efliciency. While the modulation ca- 5, pability of the transmitter may run up to 100 percent, the efliciency of the power stage will at most be 35l percent at low modulation percentages.

Methods have been disclosed in the prior art which will insure an improvement of eiiiciency of l the power stage Y to around 60 percent. Most widelytknown are the Chireix method and plate modulation of the final stage by means, of class B-type push-pull audio ampliers.

f According to the method of this invention, efliciency of the power stage of a transmitter may be raised even beyond what'was possible with the methods of the prior art'. The underlying principle is as follows:

' The plate directcurrent and modulation p0- 9 tentials of the power stage, are furnished from a grid-controlled (grid-excited) rectifier whose feed frequency is conveniently chosen higher than the highest frequency of modulation to be trans# mitted. Since the 'regulation of the direct curu rentv potential furnished from a gaseous-conduc- 4 tion rectifier of the said type is insured by a shift of the phase of the grid impulses, in accordance with this invention the phase of the potential impulses impressed upon the grid is here varied, 3 at the rate or rhythm of the modulation. IThis type of regulation always makes forsatisfactory Y efficiency of the rectier, at all instantaneous values of its useful potential since'current is suppliedl only at small plate potential atI the recti- 35 fier.` l f In describin the invention detail reference wilibe made to the attached drawings, wherein Figure 1 shows one modiflcation of my novel modulating system wherein 'an amplifier of wave 40 energy has an electrode controlled in accordance with potentials derived 'from a rectifier having electrodes supplied by other wave energy and a control electrode supplied with still other wave 45 energy, the phase of which is controlled in accordance withmodulating potentials to control the operativeness of the rectier;'

Figures 3v and 4 are modifications f the arrangement of Figure 1. Figure 3 includes recti- 50 er means for increasing the impulses on the control grid of the rectifier per cycle of energizing current tothereby improve the linearity of operation of the modulation system Figure 4, which -is a modification of Figure 3,- includes a 55 plurality of saturated cores and cooperating Telegraphie m. b many, a. corporation of Germany 1937, Serial No. 140,13

and Rudolf Giirtler, Berlin, Gerto Telefunken Gesellschaft fr H., Berlin, Ger- April 1, 1936 windings similar to the ing 0f Figure 1; while Figure 2 illustrates the operation of the arrangement by means of curves.

' Figure 1 schematically shows an exemplifiedA 5 embodiment of the invention. S is the power stage of a telephonie transmitter whose carrier frequency may be denoted by f. The plate direct e. current potential and the modulation potential are supplied through a rectifier G which is fed from an auxiliary generator H with a fundamental. frequency V which suitably is a multiple ofthe highest modulation frequency, so as to insure modulation as free as feasible from distortion. The auxiliary 4generator or` oscillator H may be of the vself-exciting (self-oscillatory) or master excited type. In this latter case, if desired, there may be chosen ;f=V, and the control frequency' for the auxiliary generator may be taken froml a transmitter stage illustrated diagrammatically at 20, Moreover, the auxiliary, transmitter may be utilized for the control of the transmitter power stage. y If the feed potential is sinuo the phase shift `of the grid potential impulses of the rectifier should occur roughly according to a function inverse to the sine function, so as to prevent distortions, it being assumed that the inner resist' ance of the rectifier is negligible.

l Proportionality could be insured in a simpler G with peaked feed potential, and by varying the phase of the grid potential impulses in direct proportionate the instantaneous value of the Asupplied modulation potential. Now, the operation of the circuit organization 'shown in Figure 1 is as follows:` The direct current fed to tube 3 is changed into alternating current of fundamental frequency V, at, satisfactory. efficiency. The output electrodes of 3 40 are connected as shown to windings I and 2 coupled to windings 4 and 5 connected in series with the anode and cathode of rectier 1. The control grid of '1 is coupled as s hown to a winding c, of transformer I4. As will in detail later the phase of the wave energy to the grid of 1 is controlled in accordance with modulating potentials from M, in this maner controlling the output of rectifier I and the Y er S in accordance with signals. The wave form of the`potential impressed upon rectifier 1 may be renderedpaked, for instance, by providing a convenient number of resonance circuits, l and 2 in single core and windbe described more power supplied by 1 to the ampli# 50 the output circuit of tube 3 which 55 ulation potential Rectifier tube 1 may quency and to which'is coupled, with convenient closeness, the input circuit of rectifier 1 by means of coils 4 and 5. The required linear proportionality between the`modulation potential and the phase angle of the grid potential may be insured, as known in the art, by a saturated transformer I4 wrapped with three windings, a, b, and c. Winding a, is impressed with a potential through transformer 6, an impedance II being interconnected for the purpose of imparting a peaked wave form to the current flowing through winding a. Transformer I4 is saturated to such a high degree that pointed or peaked potential impulses are induced in the winding c, and these impulses will arise when the resultant ampereturns pass through zero. This produces a negative impulse at the greatest rate "of decrease of the flux, and a positive impulse at the greatest rate of increase of the ux, and in this case only the-,positive pulse is able or useful toy cause the gaseous rectifier to pass current. This is shown in the curves of Figure 2. This impulse then takes place when the feed potential has passed its peak. It should be kept in mind that the feed potential or Voltage, supplied by tube 3 to windings 5 and 4 and rectifier 'I, is in phase with the'peaked current in winding a, of the highly saturated transformer I4. The vol age induced in winding c is rising then at its greatest rate when the peak of the feed potential to 'l has passed. Thus the grid of 1 gets a potential which causes it to pass current when the feed voltage has passed its peak. The separation of this grid impulse from the peak of the feed potential from 'I is a function of the saturation of transformer I4 and consequently of the modulating potentials so that the output of l is likewise a function of the modulating potentials. Winding bis energized by adire'ct current through potentiometer'IZ which, in the-absence of modulation, determines the4 phase of the grid potential impulses and thus the value of the direct, current potential furnished by rectifier 1. Through transformer I3 is supplied a modulation potential which varies the vzero value of the resultant ampere-turns at the rhythm of the modulaton in such a manner `that proportionality exists between the phase of thegrid Vimpulses and the instantaneous value of the modulation potential. Auxiliary Wave V and its harmonics are Vsuppressed by band-pass filter comprising condensers 8 and I0 and inductance 8 with the result that only the direct potential and the modwill reach the transmitter.

consist of a high-vacuum tube or kenotro'n, or, preferably, because of lower,

Y 'internal resistance, of a gas-filled rectifier (for instance, an iron rectifier). It will be understood that in lieu- 0f rectifier 'I a multi-phase rectier circuit scheme could be used.

The embodiment .according to Figure 1, and similar circuit organizations; have the peculiarity that the load putby rectifier G on the auxiliary generator H involves a reactive component whose 'value varies'with 'the instantaneous value of the modulation potential, and tins-ofrece. the

' emciency of the'rectiijier.

Using rectiers having a steady characteristic, that is to. say, electronic rectiers or kenotrons and which, contradistinct to the gaseousconduction type, may be steadily controlled (excited)` u p and down, the chance of complex load conditions may be mental harmonic prevented for the fundaof the feed frequency by doulof rectifier there will now produce two lthe eciency of the bling the positive grid potential impulses so that, at all instantaneous values of the modulation potential, they will act symmetrically, as to time, with respect to the crest of the feed alternating potential.

In Figure 2 are indicated the peaked rectifier feed potential and thereunder the grid impulses supplied to the rectifier. As shown therein one grid impulse is supplied to the rectifier when it is a gaseous conduction rectifier,4 and two impulses when it is a thermionic high vacuum rectifier. That is to say, with the former type be only one grid impulse applied each half period or alternation of the feed potential, which impulse will,

therefore, be non-symmetric to the crest of the feed potential, whereas it, is advantageous with thermionic rectifiers to produce one grid impulse before and one grid impulse after the feed potential crest, as shown in the drawings. By the modulation potential in the case of gaseous-conduction rectiers, the single grid impulse is shifted to and fro in phase In the case of thermionic rectiers the modulation potential affects the interval between the two grid impulses Figures 3 and 4 show in schematic manner exemplified embodiments of a grid control of the said kind. Contradistinct` to the arrangement in Figure 1, the embodiment in Figure 3 shows winding c of transformer I4 with a center tap. In addition, two rectiers I5 and I 6 are arranged in a, circuit with winding c to cause the two impulses occurring symmetrically relative to the feed potential crest to produce positive grid potential. It is necessary in this case that the current flowing through winding a should be in phase with the feed voltage at transformer 6.

In Figure 3 the rectifier 1 is of a type having a steady characteristic controllable by controlling its grid potential.

positive impulses occurring of the flux of transformer I4 is greatest and when the increase of the flux of transformer I4 is greatest. Note that negative impulses are ineffective. Here again the feed potential for 'l is in phase with the peaked cur- When the decrease krent in a and consequently the positive pulses ulating potential at I3.

In the case of quadrature relation said two quantities, recourse may be had to a scheme shown in Figure 4,- which comprises two transformers I4 and I 4' whose operation is similar to that described above. While windings b and b are traversedin opposite sense by direct and modulation currents, -the windings a,- a'. and c, c', respectively, are connected in the same sense. A

The ldoubling of the active gridfimpulses as just described has this further advantage that rectifier, for agiven transmitter load, rises Vappreciably for the reason that the duration or length of current feed or W periods during grid impulses decreases correspondingly. The same method may, of course, be used again also with multi-phase rectifier circuit organizations.`

' Thgwwer Stage etilciency obtainab1- e. at the between the aziende 3 present state'orv the art, with an arrangement pllfying device having input electrodes and output oi this invention is higher than that of the methelectrodes connected in alternating current cirod disclosed and known fin the earlier art and cuits wherein high frequency wave energy flows vdesigned to raise -the enlciency. Assuming the andmeans iorapplying to an electrode of said following unit eillciencies, namely 90% for the device a potential lwhich variesvat signal fre- 5 auxiliary generator, 98% for the rectiiier (asquency to thereby modulate said high frequency suming that ignition or discharge type recti. 'wave energy msgid device'and circuits 1n accord. ners are/used) 80% for the power stage, then ance with signals comprising, a rectiiier tube havthe overall eiliciency of the power stage will be ing a control electrode and a pair'of additional l0 about 70%: and this high eiilclency would be electrodes coupled'with said electrode in said am-,10 preserved also with highpercentage modulations. piiner device, means for impressingwave energir Itis claimed: l. In a modulation system, anelectron dispotentials are impressed from said additional charge device having input electrodes excited by electrodes on said electrode of` said amplier dewave .energy to be modulated and. output elecvice when said rectierisoperative, means for im- 15 trodes connected in an output circuit; and means pressing wave energy of the same frequency as ior modulating the wave energy at signal fre` said last named wave energy on the-'control eleci quency comprisingv a rectifier having output electrode of said rectiiier to control vthe operation of A trodes connected with electrodes in said device said rectiii'er and for controlling the phase of the to energize the same to control the operation of' wave 'energy impressed on said control electrode 20' said device, said rectifier having input electrodes in accordance with modulating potentials to and a controlling electrode, a source of wave thereby control the amplitude o! theA potentials energy coupled to said input electrodesa trans `supplied Yfrom the additional electrodes of said former having a plurality of windings; a coupling rectifier to said electrode in said amplifier device between said last named source and one of said comprising, a saturated core, a plurality of lwindf- 25 windings, a coupling betweenl the rectier input ings on said core, a source of modulating potenl electrodes and another of said windings and tials connected `to a winding on said core to conmeans for controlling the saturation o! .said -txol the saturation thereof, means for energizing transformer atsignal frequency to control the one 'of said windings by wave energy of said same phase relation ofthe vvave energy on the controllfrequency, and means connecting another ol' said 30 ing electrode land input of said rectifier to thereby windings' to said control electrode of said rectiiier. control the energy supplied to said electrodes in 4. In a signalling system, an electron discharge said device. v Y device having input and output electrodes cou- 2. In a modulation system, a wave energy ampled in high frequency alternating current cirpliiying device having input electrodes and output cuits in which high frequency wave energy to be electrodes connected in alternating current cir' modulated is caused to ilow and means for moducuits wherein high frequency wave energy iiows latins the potentials of certain of said electrodes and means for applying to an electrode oi said at frequency to thereby control the amplidevice al potential which varies at signal iretude of the high frequency wave energy in accord- 4o quent-,y to thereby modulate said nigh frequency ance with signals ecmpnsing, aer'navlng a i wave energy in said device and circuits in accontrol grid and having ananode and a cathode, cordance with signals comprising, a rectier tube means for y wave energy of rectilinear having a' control electrode and a pair of addiform and impressing the same on the anode and tional electrodes coupled with said electrode in cathode of said reclziiiei. means for impressin 4,5 saidv ampliiler device means for impressing waveve energy of the frequency'orvsaid produced 4s energy onsaid additional electrodes whereby recve. energy on the control grid ot said rectifier tied 'potentials are impressed from said addiand for controlling the phase of said last named tional electrodes on said electrode of said ampliim wave energyin accordancewith signaliler device when said rectier is operative, means ling `potentials comprising, a saturated transfor impressing wave energy oi the same frequency former core, a winding on said core,A means for n as said last named wave energy on the control ene d a electrode of said rectifier to control the operation frequency oisaid produced wave energy, a second of said rectiner comprising, a satmated core," winding on said core connected to said control windings thereon, means for supplying said wave electrode o! said rectiiiel' to impress thereon wave energy to one oi.' said windings on' said core, a full energy o! the frequency of said wave .g wave rectiiler having an output connected to said energy, a source ot potentials. and .contol electrode and an input coupled to a windmeans for controlling time saturation of said core ing n said saturated core, and means for conin accordance with potentials from said trolling the phase of said wave energy impressed .to thereby control tgedpbae o! said wave trol the amplitude o! the potentials supplied lfrom thorvle 0f the gg:

' in d v Y v Il the additional electrodes of said rect er to sai l mme mode andmngthode of md der on electrodes of said device to controlthe opa ten eration thereof at signal frequency. between an additional ding on seid saturated n YH :u HH t core and said source of modulating potentials.

3. In a modulation system. a wave amy RUDOLF 'GR'nm 

